Fluid dispensers are commonly found in household or engineering applications such as perfume bottles, cosmetic foams, pharmaceuticals, disinfectant or oil or paint dispensers or others such as aerosol canisters.
Typically a fluid in a container is pushed out due to a pressurized propellant such as a gas pre-filled or pumped into the container, or the fluid is drawn out by a pump or a squeeze.
In some ordinary cases the dispensers have a continuous operation, that is, as long as a release valve is activated the fluid is expelled. In other cases the dispensers operation is intermittent, that is, some volume is delivered in a manner responsive to pumping or squeezing.
In some applications, for example therapeutical applications, the dispensed quantity or volume of the fluid has to be controlled. Various mechanisms were proposed for delivering fixed or variable controlled quantities. For example, U.S. Pat. No. 3,878,973 relates to a piston-cylinder with a metering valve, U.S. Pat. No. 6,702,155 that relates to metering a dose by a plunger operated by a wheel, U.S. Pat. No. 4,033,487 that relates to a dispenser with double-handled trigger where each handle releases a pre-set dose, U.S. Pat. No. 6,257,457 that relates to a device for spraying fluid in a tank with a fractioning means to fraction the fluid into doses, or U.S. Pat. No. 5,085,351 that relates to releasing an predetermined quantity from a pressurized reservoir.
Generally, in a dual or multiple metered doses dispenser, the user has to perform some special operation in order to select between two or more doses or to set the dose to be released. For example, pressing different triggers or rotating a wheel, may require maneuvering the position of the container, the hands or the fingers.
Typically fluid is delivered out of a dispenser via a narrow outlet such as a nozzle. Often, after dispensing a fluid, some fluid residues remain in the nozzle and may dry out or otherwise change, resulting in clogging or obstructing the passage of fluid in and out of the nozzle. Some mechanisms were proposed for cleaning a nozzle. For example, U.S. Pat. No. 5,255,848 relates to a multiple orifice spray nozzle having reversible orifice cleaning, U.S. Pat. No. 6,634,570 that relates to a needle that pushes into the nozzle under spring force, or US 2006/0030509 that relates to exchanging the fluid container with a cleaner container to release the cleaner fluid via the nozzle.